Sheet stacking apparatus and sheet processing apparatus equipped therewith

ABSTRACT

A sheet stacking apparatus includes: a stacking tray which stacks a fold-processed and ejected sheet, and descends in response to a mass of stacked sheets; and a first sheet pressing member which holds the stacked sheets downward from an upper side of the stacked sheets at a constant height.

This application is based on Japanese Patent Application Nos.2007-163536 filed on Jun. 21, 2007, 2007-164803 filed on Jun. 22, 2007,and 2007-164804 filed on Jun. 22, 2007, which are incorporated hereintoby reference.

BACKGROUND OF THE INVENTION

The present invention relates to a sheet processing apparatus forconducting a fold processing of a sheet, particularly, relates to animprovement of a sheet ejection section in a small size sheet processingapparatus for conducting the fold processing of a sheet, onto which animage has been formed, by combining an image forming apparatus.

With respect to the ejection section in the image forming apparatus anda sheet processing apparatus, the improvement of stacking sheets onto astacking tray in the sheet ejection sections of the image formingapparatus in perfect order has been conducted.

The fold-processed sheet tends to become irregular and tends to beirregularly stacked in the sheet ejection section comparing with a flatshaped sheet, to which the fold process has not been applied.

Particularly, in the case of the sheets, to which a multiple-fold suchas three-fold has been applied, for example, the sheets, to which themultiple-fold such as a gatefold or a double-parallel fold has beenapplied, there is a case that the sheets are deformed into a completelydifferent style from a flat plate shape, stacked irregularly in thestacking section and scattered out from the stacking section.

Hitherto, the fold-processed sheets have only been stacked into a boxshaped tray. The sheets have been irregularly stacked into the stackingtray.

Unexamined Japanese Patent Application Publication Nos. 2002-255431 and2001-26360 disclose technologies for putting the fold-processed sheetsin order.

According to the technology disclosed in Unexamined Japanese PatentApplication Publication No. 2002-255431, a roller provided at the edgeof the arm, which is capable of freely rotating, and a paddle, which iscapable of freely rotating, hold two points of the sheets to be stackedin order to stack the fold-processed sheets onto the stacking tray.

According to the technology disclosed in Unexamined Japanese PatentApplication Publication No. 2002-26360, a sensor is arranged to detectthe uppermost surface of stacked sheets and to lower the stacking traywhen the uppermost surface rises.

In the case of the technology disclosed in Unexamined Japanese PatentApplication Publication No. 2002-255431, since both of the two holdingmembers move up and down, the sheets cannot be stacked in perfect orderin the sheet stacking operation where the sheets tend to bulge and theuppermost surface of the sheet to be stacked is able to move up and downjust like a fold-processed sheet.

Further, the stacking apparatus disclosed in Unexamined Japanese PatentApplication Publication No. 2002-255431 does not have a moving mechanismof the stacking tray corresponding to a stacking amount. Thus thestacking apparatus in Unexamined Japanese Patent Application PublicationNo. 2002-255431 is not suitable for stacking a large volume of sheets.

According to the technology disclosed in Unexamined Japanese PatentApplication Publication No. 2001-26360, it allows the stacking tray tostack a large volume of sheets by lowering and raising the stacking trayby utilizing a motor drive.

According to the mechanism for lowering and raising the stacking tray bya motor drive, which has been disclosed in Unexamined Japanese PatentApplication Publication No. 2001-26360, a sensor detects the uppermostsurface of the sheets and the detected signal controls the motor.

According to the control described above, in the case of stacking thefold-processed sheets, there is a problem that erroneous operations tendto occur due to sheet bulge. Also there is a problem that lack ofstability and reliability of the operation occurs.

Further, there is a problem that the motor drive makes a controlmechanism complicated and raises the cost of the apparatus.

Unexamined Japanese Patent Application Publication Nos. 2002-274727 and07-300270 disclose a technology for proving a sheet pressing member forpressing sheets downward to a place adjacent to an ejection section.

Unexamined Japanese Patent Application Publication No. 07-300270discloses a sheet presser operating member for drawing a sheet pressingmember and moving the sheet pressing member onto the upper surface of anewly ejected sheet.

According to Unexamined Japanese Patent Application Publication Nos.2002-274727 and 07-300270, the structure is not arranged to put thefold-processed sheets in order. The structure is not well designed tostack the sheets in order to stack the fold-processed sheets in order.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a sheet stackingapparatus includes

a stacking tray for stacking a fold-processed and ejected sheet, thestacking tray being arranged to descend corresponding to a mass ofstacked sheets, and

a first sheet pressing member for pressing the stacked sheets from anupper side of the stacked sheets at a constant height.

According to another aspect of the present invention, a sheet stackingapparatus includes

a stacking tray for stacking a fold-processed and ejected sheet,

a first sheet pressing member for pressing a trailing edge of a sheet inan ejection direction of the sheet at a constant height, and

a second sheet pressing member for pressing a leading edge of the sheeton the stacking tray in the ejection direction of the sheet,

wherein the second sheet pressing member is supported by a stationarysection in an upstream side edge of the sheet in the ejection directionof the sheet and a downstream side edge portion of the second sheetpressing member in the ejection direction of the sheet is a free edge.

According to still another aspect of the present invention, a sheetstacking apparatus for stacking a fold-processed and ejected sheetincludes

a sheet stacking tray for stacking a sheet

a third sheet pressing member for holding a sheet, which has beenstacked on the stacking tray, and

a control member for controlling the third sheet pressing member,

wherein the control member selectively positions the third sheetpressing member at either a place where the third sheet pressing memberpresses the sheet or a retreated place where the third sheet pressingmember has retreated from the sheet in response to at least one of asheet size, a sheet kind, and a kind of fold processing.

According to yet still another aspect of the present invention, a sheetstacking apparatus including a fold processing section for conducting afold processing of a sheet, an ejection section for ejecting afold-processed sheet and a sheet stacking apparatus for stacking thesheet, which has been ejected from the ejection section, the sheetstacking apparatus includes,

a stacking tray, which is capable of descending in response to a mass ofstacked sheets, to which the fold process has been applied and ejectedfrom the ejection section, and

a sheet pressing member for pressing the stacked sheets from an upperside of the stacked sheet at a constant height.

According to yet still another aspect of the present invention, a sheetprocessing apparatus including a fold processing section for conductinga fold processing of a sheet, ejection rollers structured by a pair ofrollers, an ejection section for ejecting a sheet processed by the foldprocessing section, and

a sheet stacking apparatus for stacking a sheet ejected from theejection section, the sheet processing apparatus includes,

a stacking tray for stacking a sheet, to which the fold process has beenapplied by the fold processing section and ejected from the ejectionsection,

a first sheet pressing member for pressing a trailing edge of the sheetin an ejection direction of the sheet at a constant height, and

a second sheet pressing member for pressing a leading edge of the sheeton the stacking tray in the ejection direction of the sheet,

wherein the second sheet pressing member is supported by a stationaryshaft section in an upstream side edge portion of the sheet in anejection direction of the sheet and a downstream side edge portion ofthe second sheet pressing member in the ejection direction of the sheetis a free edge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a total drawing of an image forming system having asheet processing apparatus related to an embodiment of the presentinvention.

FIG. 2 illustrates a total structure drawing of a sheet processingapparatus B of the present invention.

FIGS. 3( a)-3(f) illustrate examples of fold processes.

FIG. 4 illustrates a cross sectional view of a sheet stacking apparatusrelated to an embodiment of the present invention.

FIG. 5 illustrates a cross sectional view of a sheet stacking apparatusrelated to an embodiment of the present invention.

FIG. 6 illustrates a perspective view of a sheet stacking apparatusrelated to an embodiment of the present invention.

FIG. 7 illustrates a relationship between ejection rollers and a rotarymember of the sheet processing apparatus.

FIG. 8 illustrates a cross sectional view of the sheet stackingapparatus related to the other embodiment of the present invention.

FIG. 9 illustrates a cross sectional view of the sheet stackingapparatus related to the other embodiment of the present invention.

FIG. 10 illustrates a perspective view of the sheet stacking apparatusrelated to the other embodiment of the present invention.

FIG. 11 illustrates a relationship between ejection rollers and a rotarymember of the sheet processing apparatus.

FIG. 12 illustrates a cross sectional view of the sheet stackingapparatus related to the other embodiment of the present invention.

FIG. 13 illustrates a cross sectional view of the sheet stackingapparatus related to the other embodiment of the present invention.

FIG. 14 illustrates a perspective view of the sheet stacking apparatusrelated to the other embodiment of the present invention.

FIG. 15 illustrates a relationship between ejection rollers and a rotarymember of the sheet processing apparatus.

FIG. 16 illustrates a cross sectional view of the sheet stackingapparatus related to the other embodiment of the present invention.

FIG. 17 illustrates a plan view of the sheet stacking apparatus relatedto the other embodiment of the present invention.

FIG. 18 illustrates a block diagram of a control system of an imageforming system having a sheet processing apparatus related to anembodiment of the present invention.

FIG. 19 illustrates a flowchart for a control of a sheet pressingmember.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be described by using embodiments of thepresent invention. However, the present invention is not limited to theembodiments.

FIG. 1 illustrates the total drawing of the image forming system havinga sheet processing apparatus pertaining to an embodiment of the presentinvention.

[Image Forming System]

An image forming system includes an image forming apparatus A, anautomatic document feeder DF, a sheet processing apparatus B and a largecapacity tray LT.

An image forming apparatus A illustrated in FIG. 1 includes an imagereading section (an image input apparatus) 1, an image processingsection 2, an image writing section 3, an image forming section 4, asheet feed cassettes 5A, 5B and 5C, a manual feed tray 5D, a first sheetfeed sections 6A, 6B, 6C, 6D and 6E, a second sheet feed cassette 6F, afixing unit 7, an ejection section 8 and an automatic duplex unit (ADU)8B.

The automatic document feeder DF is provided on the top of the imageforming apparatus A. The sheet processing apparatus B is connected to asheet ejection section 8 provided on the left side surface of the imageforming apparatus A illustrated in FIG. 1.

One surface or both surfaces of the document placed on the documenttable of the automatic document feeder DF is conveyed to be read by theoptical system of the image reading section 1 and read into an imagesensor 1A.

An image processing section 2 applies an analog process, an A/Dconversion, a shading correction and an image compression process to ananalog signal, to which photo-electric conversion has been applied bythe image sensor 1A. Then the signal is transmitted to an image writingsection 3.

In the image writing section 3, emitted laser beam from a semiconductorlaser is irradiated onto a photosensitive drum 4A of an image formingsection 4 and a latent image is formed on the photosensitive drum 4A. Inthe image forming section 4, processes such as charging, exposure,development, transfer, separation and cleaning are conducted. A transferunit 4B transfers an image onto a sheet S, which has been respectivelysupplied to the first sheet feed sections 6A-6E from sheet feedcassettes 5A-5C, a manual feed tray 5D or a large capacity tray LT. Afixing unit 7 fixes the image onto the sheet S, which carries the image.The sheet S is conveyed to the sheet processing apparatus B from a sheetejection section 8. Or, the image forming section 4 again applies a dualsurface image process to the sheet S, which has been conveyed to anautomatic duplex unit 8B by a conveyance path switching plate 8A. Thenthe sheet S will be ejected from the ejection section 8.

[Sheet Processing Apparatus]

The sheet processing apparatus B is configured by a sheet entrancesection 10, a sheet ejection section 20, a sheet adding section (a coversheet feeding section) 30, a punch processing section (a punchingsection, a first processing section) 40, a conveyance section 50, afolding section (a second processing section) 60 and a sheet stackingapparatus 100.

FIG. 2 illustrates a total structure drawing of a sheet processingapparatus B of the present invention.

(Sheet Entrance Section)

A sheet S, to which an image forming process has been applied by theimage forming apparatus A, is guided to the sheet entrance section 10.

The recording sheet entrance position of the sheet entrance section 10opposes to a recording sheet ejection position of the ejection section 8of the image forming apparatus A.

The recording sheet S guided to entrance rollers 11 is branched (abranching section) to either the sheet ejection section 20 or the punchprocessing section 40 by a conveyance path switching member G1.

(Sheet Ejection Section)

When a punch process and a fold processing are not set, the conveyancepath switching member G1 shuts off the conveyance path to the punchprocessing section 40 and opens the conveyance path to the sheetejection section 20.

The recording sheet S, which passes through the first conveyance path P1heading to the sheet ejection section 20, moves straight while beingnipped by the conveyance rollers 21 and 22. Then the recording sheet Sis ejected from the ejection section 20 by sheet ejection rollers 23 andstacked on a stacking tray 102 in the sheet stacking apparatus 100.

The recording sheet S, which has been branched upward in FIG. 2 in thedownstream side of the sheet conveyance direction of the conveyancerollers 22 by a conveyance path switching member G2, passes through theconveyance rollers 25 of the sixth conveyance path P6. The recordingsheet S is ejected by the sheet ejection rollers 26 and stacked onto asub-stacking tray (a top tray) 27 as a single sheet processing ejectionsection disposed upper section of the sheet processing apparatus B. Thesheet S, to which the fold processing has not been applied, is ejectedonto the sub-stacking tray 27.

(Punch Processing Section 40)

The sheet S, which has been branched by the conveyance path switchingmember G1 of the sheet entrance section 10, is nipped by the conveyanceroller 41 disposed at the lower section of the conveyance path switchingmember G1, and conveyed to a punch processing section (the firstprocessing section) 40 (second conveyance path p2).

An aligning section 42 disposed on the conveyance path of the downstreamside of the punch processing section 40 aligns the sheet width directionof the sheet S, to which the punch processing has not been applied.

A puncher of the punch processing section 40 is configured by a puncher,which is driven by a drive section (not shown), and a dice, which fitsthe blade section of the puncher. The sheet S, to which a punchprocessing has been applied, is conveyed to the downstream of aconveyance section 50 (a punching function).

(Conveyance Section 50)

The sheet S, which has been conveyed to a conveyance section 50, isnipped by the conveyance rollers 51, 52, 53 and 54 and conveyed to thefold processing section 60. The conveyance rollers 51, 52, 53 and 54 areconfigured by a drive roller, which is connected to a drive source and adriven roller, which is pressed and contacted by the drive roller. Eachdriven roller is connected with a solenoid SOL and arranged to contactto and separate from the drive roller.

The sheet S, to which no fold processing has been applied, among thesmall size sheets, to which the punch processing has been applied,passes through a third-A conveyance path 3A branched by a conveyancepath switching member G3 and conveyed while being nipped by conveyancerollers 600. The large size sheet S, to which the punch processing hasbeen applied, is conveyed to a third-B conveyance path 3B positionedunder the branch position of the conveyance path switching member G3irrespective to whether the fold processing has been applied or not.Then the large size sheet S is conveyed and guided into the foldprocessing section 60 by the conveyance rollers 53 and 54. Here, thethird-A conveyance path 3A and the third-B conveyance path 3B configurethe third conveyance path.

A conveyance path switching member 55 is provided in the conveyancesection 50. The fold processing can be conducted on two sheets at thesame time by storing and conveying two small size sheets. Further, it isapparent that it becomes possible to configure the apparatus so as toconduct the fold processing on each and every one of the sheet S withoutproviding the conveyance path switching member 55.

(Fold Processing Section 60)

The sheet S, which has been conveyed to the fold processing section (thesecond processing section) 60 from the conveyance section 50, is nippedby registration rollers 601. Then the sheet S is conveyed to a firstfold section 61, a second fold section 62 and a third fold section 63,where fold processing (folding functions) such as center-folding,Z-folding, outer-three-folding, inner-three-folding andinner-four-folding (also named gate-folding) will be conducted. Then thesheet S will be returned to the first conveyance path P1 through thefourth conveyance path P4.

FIGS. 3( a)-3(f) illustrate fold-processed sheets S, to which variousfold processes such as the center-folding, the Z-folding, theouter-three-folding, the inner-three-folding and the inner-four-folding,have been applied. FIG. 3( a) illustrates the center-folding; FIG. 3( b)illustrates the Z-folding; FIG. 3( c) illustrates theouter-three-folding; FIG. 3( d) illustrates the inner-three-folding;FIG. 3( e) illustrates the double-parallel-folding; and FIG. 3( f)illustrates gate-folding. Unexamined Japanese Patent ApplicationPublication No. 2005-15225 discloses detailed folding mechanisms.

FIG. 4 illustrates a cross sectional view of a sheet stacking apparatus100 related to an embodiment of the present invention. FIG. 4illustrates a situation where the sheet S is not on the stacking tray102. FIG. 5 illustrates a cross sectional view of the stacking apparatus100 and a situation where the sheet S is on the stacking tray 102. FIG.6 illustrates a perspective view of a sheet stacking apparatus 100. FIG.7 illustrates a relationship between sheet ejection rollers 23 and arotary member 103 of the sheet processing apparatus B.

The sheet stacking apparatus 100 is attached to the sheet ejectionsection 20 of the sheet processing apparatus B.

The sheet stacking apparatus 100 includes a frame 101, to which variousfunctional parts are attached, which will be described hereinafter.

The stacking tray 102 is supported by a frame 101 centering on a shaft102 a in the downstream side of the conveyance direction of the sheet Sin the left edge section of FIGS. 4 and 5, namely on the stacking tray102, so as to be capable of rotating.

In FIGS. 4 and 5, the right edge section of the stacking tray 102,namely, in the upstream side of the conveyance direction of the sheet Son the stacking tray 102, is hung down by a wire 105. The other edge ofthe wire 105 is connected to a pull type spring 104. The stacking tray102 is hung down at the both ends in the conveyance width direction bythe wire 105.

One end of the spring 104 is attached to the frame 101 and the wire 105is stretched around a pulley 106.

As described above, the upstream side in the sheet conveyance directionof the stacking tray 102 is held by the wire 105 so as to be capable ofmoving up and down. As described later, when the sheet S is stacked onthe stacking tray 102 and as the mass of the stacked sheets S increases,the effect of the downward force against the stacking tray 102 descendsthe stacking tray 102.

Numeral 103 is a rotary member as a first sheet pressing member, whichis attached to a shaft fixed onto a predetermined position of a frame101, which is a stationary section, so as to freely rotate. The rotarymember 103 guides the sheet S, which is ejected from the sheet ejectionsection 20 of the sheet processing apparatus B, to beneath the rotarymember 103. At the same time, the rotary member 103 is a sheet pressingmember for pressing the sheet S. The rotary member 103 touches the sheetS to be ejected and conveyed, and rotates according to the movement ofthe sheet S.

As illustrated in FIG. 7, the center of the rotation shaft 103 a of therotary member 103 is positioned in the upper side of the extended line Lfrom the nip NP formed by a pair of rollers forming the sheet ejectionrollers 23. The lower edge 103 b of the rotary member 103, which forms asheet pressing member for pressing the sheet S, is positioned in thelower side of the extended line L.

Based on the disposition and the configuration of the rotary member 103,the leading edge of the sheet S, which is ejected and conveyed from thesheet ejection section 20, hits the rotary member 103. However, sincethe center of the rotation shaft 103 a of the rotary member 103 islocated in the upper side of the extended line L and the surface of therotary member 103, which the leading edge of the sheet S hits, declinesdownward, the sheet S is securely guided under the lower side of therotary member 103.

When the sheet S has left from the sheet ejection section 20, the rotarymember 103 presses the sheet S at a constant height. Based on thepressing action of the rotary member 103, the trailing edge Sa of thesheet S is pressed down below the sheet ejection mouth of the sheetejection section 20.

As described above, the sheet S, which has been folded and ejected, issecurely stacked in a well aligned state onto the stacking tray 102 inan ejected order from the sheet ejection rollers 23 and stacked.

In order to set apart the trailing edge Sa, in the ejection direction ofthe sheet S, from the sheet ejection roller 23, it is preferable thatthe rotary member 103 be placed close to the sheet ejection rollers 23as close as possible.

When the rotary member 103 is away from the sheet ejection rollers 23,the sheet S is bent between the sheet ejection rollers 23 and the rotarymember 103 and even when the sheet S is pressed downward by the rotarymember 103, there is a case that the trailing edge Sa of the sheet willnot come apart from the sheet ejection rollers 23 and this may cause asheet ejection jam.

The distance between the sheet ejection rollers 23 and the rotary member103 is to be “D”, which is the distance between the center point “P” ofthe nip of a pair of rollers structuring sheet ejection rollers 23 (thecenter point in the sheet conveyance direction) and the shaft 103 a ofthe rotary member 103, the distance “D” is determined based on therelationship with the radius of the rotary member 103. When the radiusof the rotary member is to be “R”, according to an example, distance “D”is set about three times of radius “R”. The relationship between “R” and“D” is as is illustrated in FIG. 7.

The sheet S is continuously ejected and conveyed from the sheet ejectionsection 20.

The rotary member 103 guides the ejected sheet S downward. Then theejected sheet S runs on the stacking tray 102 in the left direction.

When the trailing edge Sa of the sheet S has left the sheet ejectionrollers 23, the trailing edge Sa of the sheet S descends due to theeffect of the rotary member 103. Then the sheet S immediately stops dueto the pressing action of the rotary member 103.

Succeeding sheet S is stacked onto the preceded sheet S, which therotary member 103 has held and pressed to move downward.

When the sheet S has been stacked on the stacking tray 102, the mass ofthe sheets S increases. Since the thickness of the stacked sheetsincreases, the sprig 104 extends corresponding to the increase of themass of the sheets S. As a result, the right edge section of thestacking tray 102 descends.

Even when the folding condition of the sheet S is irregular, the rightedge section of the stacking tray 102 descends corresponding to the massof the sheets S. Thus, the stacking tray securely descends in responseto the stacked amount of the sheets S.

Since the uppermost surface of the stacked sheets S is pressed by thepressing surface of the rotary member 103 at a constant height, thephenomenon that the stacked sheets largely bulge can be prevented.

When the right edge section of the stacking tray 102 has reached to thelowest limit position, an actuator 108 rotates and a sensor SE providedin the sheet processing apparatus B detects the rotation. Then, the fullfilling of the sheets is notified.

Based on the full filling detection signal, the display section of theimage forming system (not shown) displays an instruction for taking outsheets from the stacking tray and the operation stops at the same time.

FIG. 8 illustrates a cross sectional view of the sheet stackingapparatus 100 of an embodiment of the present invention, where the sheetS is not on the stacking tray 102. FIG. 9 illustrates a cross sectionalview of the sheet stacking apparatus 100 of an embodiment of the presentinvention, where the sheet S is on the stacking tray 102.

FIG. 10 illustrates a perspective view of the sheet stacking apparatus100. FIG. 11 illustrates a relationship between sheet ejection rollers23 and a rotary member 103 of the sheet processing apparatus B.

The sheet stacking apparatus 100 is attached onto the sheet ejectionsection 20 of the sheet processing apparatus B.

The sheet stacking apparatus 100 includes a frame 101, onto whichvarious kinds of functional parts have been attached, which will bedescribed below.

The frame 101 supports the stacking tray 102 at the shaft 102 a of theleft edge section in FIGS. 8 and 9 so as to be capable of rotatingcentering on the shaft 102 a.

One end of the wire 105 is attached onto the right edge section of thestacking tray 102 and the other edge of the wire 105 is connected to thepull type spring 104 as shown in FIG. 8.

One end of the spring 104 is attached to the frame 101 and the wire 105is stretched around a pulley 106.

As described above, the right edge section of the stacking tray 102 isheld by the wire 105 so as to be capable of moving up and down. Asdescribed later, by the sheet S stacked onto the stacking tray 102, theeffect of the downward force against the stacking tray 102 descends thestacking tray 102.

Numeral 103 is a rotary member as a sheet pressing member, which isattached to a shaft fixed on a predetermined position of a frame 101,which is a stationary section, so as to freely rotate. The rotary member103 structures the first sheet pressing member for pressing the sheet Sejected from the sheet ejection section 20 of the sheet processingapparatus B. The rotary member 103 touches the sheet S to be ejected andconveyed, and rotates according to movement of the sheet S.

As illustrated in FIG. 11, the center of the rotation shaft 103 a of therotary member 103 is positioned in the upper side of the tangential lineL drawn at the nip NP between a pair of rollers forming the sheetejection rollers 23. The lower edge 103 b of circumference of the rotarymember 103, which presses and guides the sheet S, is positioned in thelower side of the tangential line L.

Based on the disposition and the configuration of the rotary member 103,the leading edge of the sheet S, which is ejected from the sheetejection section 20, hits the rotary member 103. The sheet S is securelyguided beneath the rotary member 103 after the leading edge of the sheetS hits the rotary member 103.

As described above, the rotary member 103 presses and holds the sheet Sby the pressing surface including the lower edge 103 b having a constantheight.

Numeral 107 denotes a pressing sheet as a second sheet pressing member.

The pressing sheet 107 includes a layered structure formed bypolyethylene sheet whose lower surface, which contacts the sheet S, hasbeen roughed and a PET (polyethylene terephthalate) sheet as a lininglayer. The pressing sheet 107 is a sheet shaped member having an elasticcharacteristic. The right edge section of the pressing sheet 107, whichis in the upstream side of the ejection direction of the sheet S, isfixed onto the frame 101. On the other hand, the left edge of Figure,which is positioned downstream side of the ejection direction of thepressing sheet 107, is movable. The surface, which contacts the sheet Sof polyethylene, is formed into a rough surface having a frictionresistor so as to prevent the sheet S to protrude from the stacking tray101. The PET sheet enhances the rigidity of the pressing sheet 107 andstrengthens the pressing action against the sheet S.

A rigid body sheet, which is supported so as to be capable of freelyrotating as a pressing sheet 107 and biased by a spring, may also beused.

The left edge of the pressing sheet 107 is a free edge and the centerportion of the stacking tray 102 is cut out as illustrated in FIG. 10.Therefore, when there is no sheet S on the stacking tray 102, the leftedge of the pressing sheet 107 crosses the stacking tray 102 and extendsdownward beyond the stacking tray 102 (referring to FIG. 8).

When the sheet S has set apart from the sheet ejection section 20, thetrailing edge Sa of the sheet S is pressed down below the ejection sheetmouth by the pressing action of the rotary member 103.

The conveyance of the sheet S is regulated to the left direction by thepressing 107. At the same time, the floating of the leading edge Sb ofthe sheet S is also regulated by the pressing sheet 107.

According to a kind of fold processing, there is a case that the sheetS, on which a multiple layered section is formed at the leading edge ofthe sheet in the conveyance direction by the fold processing, or thereis a case that the sheet S, on which a multiple layered section isformed at the trailing edge of the sheet in the conveyance direction bythe fold processing, is stacked. However, the floating of the multiplypiled section in the leading edge section can be regulated by thepressing sheet 107, and the floating of the multiply piled section inthe trailing edge can be regulated by the rotary member 103.

As described above, the folded sheet S is piled on the stacking tray 102in the ejected order from the stacking tray sheet ejection section 20and stacked in an aligned state.

The pressing sheet 107 as illustrated in FIG. 8, when no pressing sheetS is on the stacking tray 102, the pressing sheet 107 is arranged tocross the stacking tray 102 and extends to lower side of the stackingtray 102. Thus, the sheet S can be securely stacked on the stacking tray102 in an aligned state from the level where the number of sheets S issmall.

In order to set apart the trailing edge in the ejection direction of thesheet S from the sheet ejection rollers 23, it is preferred to place therotary member 103 and the sheet ejection rollers 23 close by as much aspossible.

The sheet S is continuously ejected and conveyed from the sheet ejectionsection 20.

The ejected sheet S is guided by the rotary member 103 in the downwarddirection and runs on the stacking tray 102 in the left direction alongthe lower surface of the pressing sheet 107.

When the trailing edge Sa in the ejection direction of the sheet S hasleft the sheet ejection rollers 23, the trailing edge Sa of the sheet Sdescends due to the effect of the rotary member 103. Then the sheet Simmediately stops due to the pressing action of the pressing sheet 107.

Succeeding sheet S is stacked on the preceded sheet S, which the rotarymember 103 has held and pressed to move downward.

As described above, since the sheet S securely leaves the sheet ejectionrollers 23 just after the sheet S has been ejected, in the case ofcontinuous ejection, a succeeding sheet is ejected and surely placed onthe preceding sheet. The sheet is securely piled in ejected order on thestacking tray 102. Thus, sheets S are securely stacked in the ejectionorder from the sheet ejection section 20 and a page order will not beout of order when being stacked.

When the sheets S have been stacked on the stacking tray 102, the massof the sheets S increases and the thickness of the stacked sheets alsoincrease. Thus, the right edge section of the stacking tray 102descends.

When the right edge section of the stacking tray 102 has reached to thelowest limit position, an actuator 108 rotates and a sensor SE providedin the sheet processing apparatus B rotates and detects the rotation.Then, the full fill of the sheets is notified.

Based on the full filling detection signal, the display section of theimage forming system (not shown) displays an instruction for taking outsheets from the stacking tray and the operation stops at the same time.

FIG. 12 illustrates a cross sectional view of the sheet stackingapparatus 100 of an embodiment of the present invention, in which thereis no sheet S on the stacking tray 102. FIG. 13 illustrates a crosssectional view of the sheet stacking apparatus 100, in which there isthe sheet S on the stacking tray 102. FIG. 14 illustrates a perspectiveview of the sheet stacking apparatus. FIG. 15 illustrates a relationshipbetween sheet ejection rollers 23 and a rotary member 103 of the sheetprocessing apparatus B.

The sheet stacking apparatus 100 is attached to the sheet ejectionsection 20 having a pair of sheet ejection rollers 23 of the sheetprocessing apparatus B.

The sheet stacking apparatus 100 includes a frame 101, to which variousfunctional parts are attached, which will be described hereinafter.

The stacking tray 102 is supported by the frame 101 on a shaft 102 a, atthe left edge portion of FIGS. 12 and 13 so as to be capable ofrotating.

One end of the wire 105 is attached to the right edge portion of thestacking tray 102 in FIGS. 12 and 13, and the other edge of the wire 105is connected to the pull type spring 104.

One edge of the spring 104 is attached to the frame 101 and at the sametime the wire 105 is stretched around a pulley 106.

As described above, the right edge section of the stacking tray 102 isheld by the wire 105 so as to be capable of moving up and down. Asdescribed later, since the sheet S is stacked onto the stacking tray102, the effect of the downward force against the stacking tray 102descends the stacking tray 102.

Numeral 103 denotes a rotary member attached to the shaft fixed on theframe 101 so as to be capable of freely rotating. The rotary member 103guides the sheet S, which has been ejected from the sheet ejectionsection 20 of the sheet processing apparatus B, and structures a firstsheet pressing member for pressing the sheet S. The rotary member 103contacts the sheet S and rotates according to the movement of the sheetS.

As illustrated in FIG. 15, the center of the rotation shaft 103 a of therotary member 103 is positioned in the upper direction of the tangentialline L drawn at the nip NP in between a pair of rollers forming thesheet ejection rollers 23. The lower edge 103 b of the circumference ofthe rotary member 103, which presses and guides sheet S, is positionedin the lower direction of the tangential line L.

Based on the disposition and the configuration of the rotary member 103,the leading edge of the sheet S, which is ejected and conveyed from thesheet ejection section 20, hits the circumference of the rotary member103. After the sheet S hits the circumference surface of the rotarymember 103, the sheet S is securely guided beneath the rotary member103.

Numeral 207 is a third sheet pressing member for pressing the sheet S.The third sheet pressing member 207 is structured by a leading edgestopper 207 a, which regulates the protuberance of the leading edge ofthe sheet S, and a sheet pressing section 207 b for pressing sheet Sfrom the above of the sheet S.

The leading edge stopper 207 a is parallel with a trailing edge supportwall 101 a for supporting the trailing edge in the conveyance directionof the sheet S on the stacking tray 102 formed on the frame 101.

As described above, due to the structure that the leading edge stopper207 a is parallel with the trailing edge support wall 101 a, the sheet Sis stacked on the stacking tray 102 in perfect order without bending.

Here, “parallel” does not mean that the angle formed by two lines isprecisely 180° but also includes a case where the angle formed by twolines is slightly off from 180°.

The third sheet pressing member 207 is capable of moving to a retreatedposition, which is illustrated in a dotted line, and a pressingposition, which is illustrated in a solid line.

The leading edge of the sheet S, which is ejected from the sheetejection rollers 23, contacts the rotary member 103. Then the leadingedge of the sheet S is guided beneath the rotary member 103. As theleading edge of the sheet S comes in contact with the third pressingmember 207, the sheet S is stopped.

The rise of the leading edge in the conveyance ejection direction of thesheet S is regulated by the sheet pressing member 207 b and, at the sametime, extend to the downstream in the conveyance ejection direction willbe prevented by the leading edge stopper 207 a.

The trailing edge of the sheet S is pressed downward by the rotarymember 103 just after the sheet has left the sheet ejection rollers 23.

As described above, the sheet S is stacked on the stacking tray 102 inaligned state as illustrated in FIG. 13.

When executing a continuous ejection operation, as the successive sheetS is guided by the rotary member against the preceded sheet S stacked onthe sheet stacking tray 102, the leading edge stops at the step wherethe leading edge contacts the third sheet pressing member 207 and piledon the preceded sheet S.

As described above, the sheets S are stacked in the ejected order fromthe sheet ejection rollers 23 and a page order will not be out of orderwhen stacked.

In response to the increase of stacking amount, the right edge sectionof the stacking tray 102 descends. However, when the stacking amount hasreached the maximum stacking amount, the stacking tray 102 presses androtates the actuator 109. Then, the sensor SE detects the rotation andoutputs the full fill signal.

FIGS. 16 and 17 illustrate the other embodiments of the presentinvention. FIG. 16 illustrates a front cross sectional view and FIG. 17illustrates a plan view of the sheet stacking tray 102.

In the embodiments, a leading edge sheet pressing member for pressingthe leading edge in the conveyance direction of the sheet is provided.The members other than the leading edge sheet pressing member are thesame as the embodiments illustrated in FIGS. 12-15.

As illustrated in FIG. 16, the pressing sheet 107 as a leading edgesheet pressing member presses the leading edge of the sheet S ejectedfrom the sheet ejection rollers 23 and regulates the bulge of thestacked sheets S.

There are various kinds of forms of the fold-processed sheet S. Forexample, in the case of the Z-folding as illustrated in FIG. 3( b), thesheet S is ejected with the top edge portion, which has an overlappedportion formed by the folding of the sheets, the front section of thesheet S tends to bulge.

In the case of this kind of sheet, the pressing sheet 107 regulates therise of the leading edge of the sheet S. At the same time, the sheetpressing member 207 also regulates the leading edge. Thus, the sheets Sare stacked on the sheet ejection tray 102 in an aligned state.

The pressing sheet 107 includes a layered structure formed bypolyethylene sheet whose lower surface contacts with the sheet S and hasbeen roughed, and a PET (polyethylene terephthalate) sheet as a liningmember. The right edge section of the FIG. 16 in the upstream side ofthe ejection direction of the sheet S, is fixed onto the frame 101. Theleft edge of pressing sheet 107, which is positioned downstream side ofthe ejection direction of the sheet, is movable. The surface, whichcontacts the sheet S of polyethylene, is formed into a rough surfacehaving a friction resistor so as to prevent the sheet S to protrude fromthe stacking tray 101. The PET sheet enhances the rigidity of thepressing sheet 107 and strengthens the pressing action against the sheetS.

A rigid body sheet, which is supported so as to be capable of freelyrotating and biased by a spring, may also be used as a pressing sheet107.

FIG. 18 illustrates a block diagram of a control system of an imageforming system and FIG. 19 illustrates a flowchart of a control for asheet processing apparatus.

The sheet pressing member 207 positions at the retreated position asshown by a dotted line in FIG. 12 before starting the operation of thesheet processing apparatus B.

Based on an operation command transmitted from the image formingapparatus A (STEP 1), determination of whether it corresponds to M or Nis conducted in STEP 2.

TABLE 1 Other than Multiple multiple folding folding Thin sheet of smallsize M N paper other than N N small size Other than thin small size N Nsheet of paper other than N N small size

In Table 1, the thin sheet of paper denotes a sheet of paper having notmore than comparative weight of 71 g/mm², the small size denotes a sheethaving a length of not more than 297 mm in a conveyance direction of asheet, to which the fold processing has not been applied yet, such as A4size, and a multiple fold denotes a folding method having not less thantriple fold, such as gate-folding and double parallel folding.

Examples in Table 1, in the case of a thin sheet of paper of not morethan A4 size, the sheet S has been stacked in perfect order bypositioning the third sheet pressing member 207 at the pressingposition.

In the case of the sheets other than the thin sheet of paper of not morethan A4 size, based on the aligning effect of the rotary member 103,even though the sheet pressing member has been retreated, sheets havebeen stacked in perfect order.

The determination illustrated in Table 1 is an example. Thedetermination illustrated in Table 1 will be modified into various ways.The third sheet pressing member 207 can be selectively positioned at thepressing position or the retreated position corresponding to at leastone of the modifications in the sheet size, a sheet kind and a foldkind.

Further, the examples illustrated in Table 1, an image forming apparatuscontroller 200 controls the sheet pressing member 107 in response to thecomparative weight of the sheet according to the kinds of sheets S.However, it is also possible to be sorted out by the rank based on thekinds of sheets S, such as a normal sheet of paper and a coated sheet ofpaper, which includes quality of a sheet of paper.

A sheet processing apparatus controller 110 communicates with the imageforming apparatus controller 200 to conducts the determinationillustrated in Table 1 in STEP 2 according to the setting in the sheettype setting section 210 a and a setting section of fold processing 210b of an operation section 210 in the image forming apparatus A.

When conducting a print operation and a fold processing based on thecommand from the external apparatus (not shown), the informationpertaining to the sheet size, the sheet kinds and kinds of foldprocessing will be given by receiving the information at a communicationsection 211 for communicating with external apparatuses.

When the sheet corresponds to M (M in STEP 2), motor 111 will beactivated (started) to set the sheet pressing member 207 at a solid lineposition as illustrated in FIG. 12 (STEP 3). When the sheet correspondsto N, the process is finished without conducting work.

When having set the third sheet pressing member 207, having conductedsheet stacking and having completed the jobs (STEP 4: YES), the motor111 is activated to return the third sheet pressing member 207 to theretreated position illustrated by a dotted line (STEP 5).

1. A sheet stacking apparatus comprising: (a) a stacking tray whichstacks a fold-processed and ejected sheet, and descends in response to amass of stacked sheets; and (b) a first sheet pressing member whichholds the stacked sheets downward from an upper side of the stackedsheets at a constant height.
 2. The sheet stacking apparatus of claim 1,further comprising a spring which urges upward and holds the stackingtray.
 3. The sheet stacking apparatus of claim 1, wherein the firstsheet pressing member guides downward the sheet being conveyed to thestacking tray.
 4. The sheet stacking apparatus of claim 2, wherein thestacking tray is pivotally supported at an edge portion of a downstreamside in an ejection direction of the sheet, and is held and urged upwardby the spring so as to be capable of moving up and down at an edgeportion of an upstream side in the ejection direction.
 5. The sheetstacking apparatus of claim 1, wherein the first sheet pressing membercomprises a rotary member which comes in contact with the sheet beingconveyed and rotates according to movement of the sheet, and pressesdownward a trailing edge of the sheets in the ejection direction, whichhave been stacked on the stacking tray.
 6. A sheet stacking apparatuscomprising: (a) a stacking tray which stacks a fold-processed andejected sheet; (b) a first sheet pressing member which presses atrailing edge of a sheet in an ejection direction of the sheet at aconstant height; and (c) a second sheet pressing member which presses aleading edge of the sheet on the stacking tray in the ejection directionof the sheet, wherein the second sheet pressing member is supported by astationary section at an edge on upstream side in the ejection directionof the sheet and an edge on downstream side of the second sheet pressingmember in the ejection direction of the sheet is a free edge.
 7. Thesheet stacking apparatus of claim 6, wherein the first sheet pressingmember comprises a rotary member which comes in contact with the sheetbeing conveyed and rotates according to movement of the sheet.
 8. Thesheet stacking apparatus of claim 6, wherein the first sheet pressingmember guides downward the sheet being conveyed.
 9. The sheet stackingapparatus of claim 6, wherein the second pressing member is a sheetshaped member having an elastic characteristic.
 10. The sheet stackingapparatus of claim 6, wherein the stacking tray is pivotally supportedat an edge portion of a downstream side in a conveyance direction of thesheet, and is urged upward by a spring at an edge portion of an upstreamside in the conveyance direction.
 11. The sheet stacking apparatus ofclaim 6, wherein when the sheet is not stacked on the sheet stackingtray, the free edge of the second pressing member protrudes downwardfrom the stacking tray.
 12. The sheet stacking apparatus of claim 6,wherein the second pressing member comprises a layer having a surface incontact with the sheet in which friction of the surface is adjusted, anda lining layer which enhances rigidity of the second pressing member.13. A sheet stacking apparatus for stacking a fold-processed and ejectedsheet comprising: (a) a stacking tray which stacks a sheet; (b) a thirdsheet pressing member which holds a sheet, which has been stacked on thestacking tray; and (c) a control member which controls the third sheetpressing member, wherein the control member selectively places the thirdsheet pressing member at either a pressing position where the thirdsheet pressing member presses the sheet or an retreated position wherethe third sheet pressing member has retreated from the sheet in responseto at least one of a sheet size, a sheet type, and a type of foldprocessing.
 14. The sheet stacking apparatus of claim 13, wherein thethird sheet pressing member comprises a leading edge stopper at which aleading edge of the sheet in an ejection direction hits.
 15. The sheetstacking apparatus of claim 13, wherein the third sheet pressing membercomprises a sheet pressing section which presses downward the sheetstacked on the sheet stacking tray.
 16. The sheet stacking apparatus ofclaim 14, further comprising a trailing edge support wall which receivesa trailing edge of the sheet stacked on the sheet stacking tray in theejection direction, and the leading edge stopper is parallel with thetrailing edge support wall.
 17. The sheet stacking apparatus of claim13, wherein the control member places the third sheet pressing member atthe pressing position when the sheet is ejected, and at the retreatedposition when the sheet is not ejected.
 18. The sheet stacking apparatusof claim 13, further comprising a first sheet pressing member whichguides the sheet when ejecting the sheet to the sheet stacking tray, andpresses downward a trailing edge of the sheets in the ejectiondirection, which have been stacked on the stacking tray.
 19. A sheetprocessing apparatus including a fold processing section which conductsa fold processing of a sheet, an ejection section which ejects afold-processed sheet and a sheet stacking apparatus which stacks thesheet, which has been ejected from the ejection section, the sheetstacking apparatus comprising: (a) a stacking tray, which is capable ofdescending in response to a mass of stacked sheets, to which the foldprocess has been applied and ejected from the ejection section; and (b)a sheet pressing member which presses the stacked sheets downward froman upper side of the stacked sheet at a constant height.
 20. The sheetprocessing apparatus of claim 19, wherein the ejection section comprisessheet ejection rollers formed by a pair of rollers, the first sheetpressing member comprises a rotary member which comes in contact withthe sheet being conveyed and rotates according to movement of the sheet,and the rotary member is arranged so that a center of a rotation shaftof the rotary member is positioned in an upper side of an extended linefrom a nip formed by the sheet ejection rollers and a sheet pressingsurface of the rotary member is positioned in a lower side of theextended line.
 21. A sheet processing apparatus including a foldprocessing section for conducting a fold processing of a sheet, ejectionrollers constituted of a pair of rollers, an ejection section forejecting a sheet processed by the fold processing section, and a sheetstacking apparatus for stacking a sheet ejected from the ejectionsection, the sheet finisher comprising: (a) a stacking tray which stacksa sheet, to which the fold process has been applied by the foldprocessing section and ejected from the ejection section; (b) a firstsheet pressing member which presses a trailing edge of the sheet in anejection direction of the sheet at a constant height; and (c) a secondsheet pressing member which presses a leading edge of the sheet on thestacking tray in the ejection direction of the sheet, wherein the secondsheet pressing member is supported by a stationary section in an edge onupstream side in the ejection direction of the sheet and an edge ondownstream side of the second sheet pressing member in the ejectiondirection of the sheet is a free edge.
 22. The sheet processingapparatus of claim 21, wherein the first sheet pressing member comprisesa rotary member which comes in contact with the sheet being conveyed androtates according to movement of the sheet, and the rotary member isarranged so that a center of a rotation shaft of the rotary member ispositioned in an upper side of an extended line from a nip formed by thesheet ejection rollers and a sheet pressing surface of the rotary memberis positioned in a lower side of the extended line.